Parts washing method with centrifugal filter

ABSTRACT

A parts washing method which utilizes a centrifugal filter to substantially reduce the need to replace its solvent. Solvent in a washing basin flows down a drain in the parts washing basin, through a screen to a centrifugal filter assembly, with a disposable filter in the filter receptacle of the centrifugal filter assembly. Thus the contaminated solvent flows from the drain, into a disposable filter element located in a spinning filter receptacle, where centrifugal force draws the solvent back into the solvent container while the materials washed from the part remain in the disposable filter element. The clean solvent is collected in a reservoir and recirculated back to the wash basin.

This application is a Divisional of U.S. patent application Ser. No.08/783,692 filed on Jan. 15, 1997, which will issue as U.S. Pat. No.5,954,071 Sep. 21, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the field of parts washing apparatusand particularly to a parts washing apparatus having a centrifugalfilter to separate foreign waste elements from a cleaning solvent.

2. Background Art

Parts washers are widely used in industrial applications, and inparticular, automotive service shops. The most familiar part washer canbe found in almost any service station in the country. It is comprisedof a sink with a spigot and a drain that sits upon a standard 45 gallondrum. The drum is partially filled with a parts washing solvent. Thesolvent is pumped from the drum, through the spigot, where it flows overthe dirty part, into the sink's drain, from which it falls back into thedrum. In this manner, the solvent continuously flows over the dirty partwhile the operator washes the part in the sink.

The problem with these conventional parts washers is that the foreignmaterial washed from the dirty part flows into the drum along with thesolvent. In many applications, the foreign material will be comprised ofmetal shavings, dirt, sand, grit, and oil particulates. Since much ofthis debris will remain suspended in the solvent while the pump isrunning, the pump is continuously subjected to substances that willdamage its internal seals. Much of the background art in this area hasaddressed this particular problem by placing a filter upstream of thepump to strain the foreign debris from the solvent before it reaches thepump. For instance, in U.S. Pat. No. 4,056,114 Boutillete), the pump issurrounded by a filter element. U.S. Pat. No. 3,890,988 (Lee) teaches apump mounted at the top of a truncated cone that rests at the bottom ofa solvent tank. The cone is made from a screen that is intended tofilter the solvent before it reaches the inlet of the pump.

In U.S. Pat. No. 3,378,019 (Riolo et al.) the patent teaches a paperfilter located below the drain. The solvent flows through the filterwith only the assistance of gravity. U.S. Pat. No. 5,522,814 (Olson)also teaches a gravity filter comprising a compartment filled with wastecotton located below the drain. U.S. Pat. No. 2,675,012 (Scales) notesthat these types of gravity filters are quickly obstructed by the gunkand will not filter the solvent. Accordingly, Scales teaches a complexset of superposed sludge settling trays of successively decreasingdiameters. U.S. Pat. No. 2,085,075 (Delano) teaches a portable crankcaseflusher and cleaner that introduces, extracts, and filters cleaningfluid from the crankcase of an automobile using a complicated reversibleone-way valve.

Trapping the gunk and the solvent together until the solvent drains fromthe filter, however, insures that the gunk will retain a substantialamount of the solvent. This wet waste material will eventually condenseinto a thick, gummy, oily substance, commonly referred to in the art as“gunk.”

The second major effect of the foreign matter flowing freely into thedrum along with the solvent is that, as the foreign material settles tothe bottom of the drum it will accumulate and condense into gunk. Thisgunk layer will eventually foul, and probably damage, the pump. In anycase, the solvent in the drum will eventually be so full of gunk andsuspended matter that it will have to be replaced and the old solventdisposed of. In the age before hazardous waste laws, this problem wasaddressed in the art by using plastic drum liners that would capture thesolvent, the foreign materials, and the gunk so that they could all bedisposed of together - - - , probably ending up in a landfill (assumingthe liner made it that far without being punctured). This disposableliner concept is taught in U.S. Pat. No. 3,890,988 (Lee). U.S. Pat. No.3,552,814 (Olson); U.S. Pat. No. 4,056,114 (Boutilette).

Contrary to a suggestion in the Lee patent, it is no longer possible toremove the gunk and solvent together in a plastic liner to be disposedof in a landfill or, for the matter, in the dirt behind the servicestation. The solvents used in parts washers are now classified ashazardous waste materials and are heavily regulated by both state andfederal law. There are severe civil and criminal penalties for theimproper disposal of the waste materials associated with these partswashers. Similarly, it is no longer practical to clean the gunk from theparts washers because the gunk still has to be disposed of as hazardouswaste.

Because of the hazardous waste laws, a huge industry has developed toservice parts washers. The 1995 annual report from the largest of theseservice providers reports reclaiming more than 210 million gallons ofcontaminated fluids and discloses revenues in this area are in excess of$240 million dollars per year. Servicing the parts washers usually meansremoving the sink from the drum, capping the used drum off, andtransporting the used solvent and gunk contained in the drum to areprocessing plant. Evidencing the major concern that the industry hasover hazardous waste liability, this service provider also advertisesthat it indemnifies the customer against liability hazardous wastespills that may occur while the solvent is being transported.

SUMMARY OF THE INVENTION

The various patents described above all address the same problem—dealingwith the separation and removal of the gunk and preventing it fromdamaging the pump. They also all share a common problem—there is no wayto stop the formation of the paste-like gunk that clogs filters,destroys pumps, and lessens the useful life of the solvent. The partswashing apparatus of the present invention significantly reduces theseproblems, and the hazardous waste problems associated with partswashers, by materially reducing the formation of the gunk by reducingthe foreign waste material that reaches the solvent tank. This is doneby employing a centrifugal filter assembly between the drain of theparts washing basin and the solvent storage tank. In this position, thecentrifugal filter removes most of the foreign particulate matter fromthe solvent before the solvent is returned to its storage container.More importantly, however, is that the centrifugal filter removes theforeign waste material from the solvent before it can condense into thepaste-like gunk at the bottom of the solvent storage tank. Instead, thecentrifugal action of the filter squeezes the solvent from the foreignwaste materials while the foreign waste material is still a small partof the solvent stream. A purified solvent is returned to the container,while the mostly-dried foreign matter is retained in the filter.

In the preferred form, a secondary “screen” filter is used at the drainof the basin to capture larger foreign objects, including componentsthat may fall off the part being washed. A tertiary filter is alsopreferably placed in communication with the solvent transfer meansbetween the pump output and the solvent inlet to “polish” the solvent byremoving any fine particles or oils that may remain suspended in thesolvent before it reaches the parts washing basin. These three filteringmeans enable the solvent to be recirculated almost indefinitely whileremaining mostly free of gunk formation.

It is important to note that most of the foreign material is captured bythe primary centrifugal filter, the secondary screen filter, andtertiary polishing filter, leaving a relatively clean solvent for reuse.In particular, these filters solve the problems associated with gunkaccumulating at the bottom of a tank. The centrifugal action of theprimary centrifugal filter spins most of the solvent out of the foreignmaterial, leaving behind a body of foreign materials captured in thefilter that is almost dry. Instead of capping off the whole solvent drumand sending it for reprocessing, the only material that need be sent toa hazardous waste facility are the disposable filters and theircontents, which can easily be placed in a canister the size of a coffeecan. This means that shipping and waste disposal fees will besignificantly less, the danger of a hazardous waste spill will beconsiderably reduced, and the cost of replacing the solvent will almostbe eliminated for most applications.

The parts washer assembly of the present invention can either beconstructed as a complete unit or, a retrofit embodiment of the presentinvention can be installed in existing parts washers to incorporate thedesign benefits taught herein. In its preferred embodiment, as acomplete parts washer, the apparatus is comprised of a parts washingbasin that rests upon a drum acting as a solvent reservoir. The washingbasin has a safety hood that is designed to drop and smother a fire ifthe fusible link holding it up is melted by a fire. The washing basinalso has a solvent transfer means, (which usually comprises a spigot,but can also be a movable hose,) an access hatch and a drain. The drainis located in the center of the access hatch and the access hatchprovides access to a centrifugal filter. The centrifugal filter assemblyis mounted below the drain of the parts washing basin with a mountingbracket. The centrifugal filter assembly comprises a filter receptacleis rotatably mounted on the mounting bracket using a sealed bearing.Operatively connected to the filter receptacle is a motor that also ismounted on the mounting bracket. A pump hangs from the mounting bracketby a pump support and is submerged in solvent that partially fills thedrum. To remove and replace the filter element located in the filterreceptacle, the access hatch is removed from the parts washing basin,exposing the filter receptacle for easy access to the filter element.The filter element is removed from the filter receptacle and stored ashazardous waste for recycling. A replacement filter element is thendraped inside the filter receptacle, with its upper edge folded over theupper edge of the filter receptacle, where it is secured to the filterreceptacle with a securing means.

In a retrofit embodiment, the mounting bracket, together with the motorand the filter receptacle are removably mounted to the underside of thesink portion of an existing parts washer. The open portion of the filterreceptacle should be positioned directly below the existing drain in thesink. The existing pump, or a new one, can be suspended from themounting bracket using the pump support described below. However, if theoriginal mounting of the existing pump does not get in the way of theretrofit assembly, it may be left in place. In either case, it ispreferable that the pump and the centrifugal filter motor be wired inparallel to a single switch 170, so that both operate when the partswasher is turned on. Given the difficulty in retrofitting an accesshatch in a existing steel parts washing basin, the hatch assembly willusually be omitted in a retrofit application. Therefore, it is importantto mount the centrifugal filter assembly of the retrofit kit to theexisting parts washing basin in a removable manner so that thecentrifugal filter assembly may be lowered and the filter element in thefilter receptacle replaced. Alternatively, most drains found in existingparts washing basins will be about four inches wide, which is usuallyenough room to reach in through the drain to remove and replace thefilter element. A secondary and tertiary filter, as described herein,are also preferably included in the retrofit of an existing partswasher.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-section view of the preferred embodiment of theparts washing apparatus of the present invention.

FIG. 2 is an enlarged portion of FIG. 1 showing the centrifugal filterassembly and mounting bracket.

FIG. 3 is a plan view looking downwardly into the parts washing basinand showing the access hatch and the drain.

FIG. 4 is a plan view taken along line 4—4 in FIG. 1 looking downwardlythrough an access hatch in the parts washing basin and showing themounting of the centrifugal filter assembly. Portions of the centrifugalfilter assembly are omitted in order to show the mounting bracket inmore detail.

FIG. 5 is a cross-section view taken along line 5—5 in FIG. 4 that omitsmost the details of the centrifugal filter assembly in order to moreclearly show the preferred manner in which the mounting bracket isattached to the underside collar of the parts washing basin.

FIG. 6 is an isometric view of the filter element used in the filterreceptacle of the centrifugal filter assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In overview, the parts washing apparatus 10 of the present invention,illustrated in FIG. 1, is comprised of a parts washing basin 12, asolvent reservoir 14 upon which the parts washing basin 12 rests, acentrifugal filter assembly 16 mounted to the parts washing basin 12below its drain 18 and inside the solvent reservoir 14, and a solventtransfer means 20 to transport the solvent 26 from the solvent reservoir14 to the parts washing basin 12. Attached to a mounting bracket 27 ofthe centrifugal filter assembly 16, and descending from it, is a pump 22that has its inlet 24 submerged in solvent 26, and its outlet 28connected to the solvent transfer means. The solvent 26 is contained inthe solvent reservoir 14.

While the parts washing apparatus 10 is in use, the pump 22 pumpssolvent 26 from the solvent reservoir 14, through the solvent transfermeans 20, where it enters the parts washing basin 12 at a solvent inlet30. From the solvent inlet 30, the solvent 26 flows over a part placedin the parts washing bin 12 or held under the inlet 30. The solvent 26is contaminated with foreign matter from the dirty part while the partis being washed. This contaminated solvent 26 flows from the partswashing basin 12, through the drain 18, into a spinning centrifugalfilter receptacle 32. The spinning action of the centrifugal filterreceptacle 32 employs centrifugal force to drive the solvent through adisposable filter element 34, after which the solvent 26 falls back intothe solvent reservoir way, the recirculation of the solvent 26 in theparts washing apparatus 10 provides a continuous flow of filteredsolvent to the parts washing basin 12 for the washing of dirty parts,while both drying and containing most the waste from the dirty part inthe disposable filter element 34.

The preferred embodiment of the present invention will now be described.The parts washing basin 12 has a sink portion 36 with an attachedflexible spout 38 acting as an inlet 30 for the solvent 26 and a drain18 acting as a solvent outlet 39. In some situations, it may be moreconvenient for the flexible spout 38 to have a connection for a flexiblehose, or merely to have a flexible hose substituted for it. The sinkportion 36 has a sink bottom wall 40 and a circumferential sink sidewall 42. For convenience of description and referring to FIG. 3, thesink wall 42 has a front portion 44 generally nearest the user, a rearportion 46 generally away from the user, a right side portion 48, a leftside portion 50, and a top edge portion 52. The top edge portion 52 isblunted or rolled over 53 so as not to present any sharp edges to theuser. The sink side wall portion 42 and the top edge portion 52 areusually formed integrally with the sink bottom 40, but separate piecesmay be attached to form the sink if easier or more cost effective.

Although the flash point of solvents used in parts washers is fairlyhigh, it is still possible for the solvent to catch on fire. Primarilyfor this reason, the rear edge 54 of a hood 56 is attached by hinges 58to the rear portion 46 of the sink side wall 42 (FIG. 1). A support pin60 is attached to an upper interior edge portion 62 of the hood 56. Afusible link 64 is rotatably attached to the support pin 60 on the hood56 and then to a support piston 66, which is then rotatably attached toa pin 67 mounted on the left sink side wall 50. The fusible link 64 isdesigned to melt during a solvent fire, which disengages the supportpiston 66 or bracket and allows the hood 56 to fall and cover the partswashing basin 12. This contains the fire and deprives it of the oxygenneed for combustion. It is preferred to use a piston for the supportbecause the hood 56 is not only used for fire prevention. During normaluse, the support piston 66 assists in smoothly lifting the hood 56, andalso preventing the hood 56 from suddenly slamming shut. Of course, ahinged bracket of conventional design could be substituted for thepiston. A work light 68 can be affixed to the hood 56 for theconvenience of the user.

The sink bottom wall 40 has an underside portion 70 located opposite theside that is contained in the sink portion 36. Attached to this sinkunderside portion 70, surrounding the drain 18, is a downwardlyextending collar 72. The collar 72 serves to position the parts washingbasin 12 on the solvent reservoir 14, to act as a splash guard for thesolvent 26 while it is being centrifuged, and as mounting point forattachment of the centrifugal filter assembly 16 and pump 22. The collar72 has several laterally extending flanges 74 attached a couple ofinches below the sink underside portion 70. To assemble the partswashing apparatus 10, the parts washing basin 12 is lowered from abovethe solvent reservoir 14 into it, inserting the collar 72 until theflanges 74 rest on the solvent reservoir 14. The spacing between theunderside 70 of the parts washing basin 12 and the flanges 74 forms anaccess portion 75 through which the transfer pipe 76 and any necessaryelectrical wiring (not shown) to drive the pump 22 and centrifugalfilter assembly 16 are placed.

In the preferred embodiment, the solvent reservoir 14 is an industrystandard forty-five gallon steel drum. However, any convenient containercould be used as long as it is capable of storing solvent in a safemanner and will support the parts washing basin at a comfortable heightfor the user.

The centrifugal filter assembly 16 is best seen in FIG. 2. Thecentrifugal filter assembly 16 is mounted to the collar 72 with amounting bracket 27, so that a filter receptacle 32 is positioneddirectly below the drain 18. The centrifugal filter assembly 16 iscomprised of a filter receptacle 32 with an open top end 80, aperforated circumferential side wall 82, and a base 84. The filterreceptacle 32 is preferably made from stainless steel, although othersolvent resistant metals and plastics may also be used. The filterreceptacle base 84 has an interior upward facing imperforate portion 86that is surrounded by the filter side wall 82 and an exterior downwardfacing portion 88. Attached to the downward facing portion is a circularmounting disk 89 that has a filter shaft 90 attached. If more convenientor economical in mass production, the circular mounting disk 89 can beomitted and the filter shaft 90 attached directly to the downward facingportion 88.

The centrifugal filter assembly 16 is attached to the collar 72 on theunderside 70 of the parts washing basin 12 using the mounting bracket 27illustrated in FIGS. 4 and 5. The mounting bracket 27 is comprised of alongitudinal member 92 and a transverse member 94 that are attached toform a cross. A sealed motor 96 is mounted to one side the transversemember 94 with its shaft 98 extending through a hole 99 in thetransverse member 94 (FIG. 2). The weight of the sealed motor 96 and thefilter receptacle 32 are approximately equal so that their respectiveweights balance the transverse member 94 at its connection with thelongitudinal member 92. While it is desirable to have this balance toease the attachment and removal of the mounting bracket 27 to the partswashing basin 12, the balance of these parts is not necessary for theproper operation of the invention because the resiliency of the mountingbracket will properly position and support the centrifugal filterassembly 16 even though they may differ significantly in weight. A motorshaft pulley 100 is then attached near the end of the motor shaft 98. Onthe opposite side of the transverse member 94, a sealed bearing 104 isattached coaxial with another opening 105. The filter shaft 90 is placedwithin the sealed bearing 104 located in the opening 105 in thetransverse member 94. A filter pulley 107 is attached to the end of thefilter shaft 90. The motor shaft pulley 100 and the filter shaft pulley107 are interconnected with a belt 102 so that, when energized, themotor 96 will spin the filter receptacle 32 about an axis with agenerally vertical orientation drawn outwardly from the interior cavity109 of the filter receptacle 32. Of course, the size of the pulleys 100,107 and the rated speed of the motor 96 will control the rate ofrotation of the filter receptacle 32. The faster this rate of spin, thegreater the centrifugal force that will be exerted on the solvententering the filter receptacle. Preferably, the filter receptacle willspin at approximately 450 to 500 revolutions per minute. At this rate ofspin, the solvent is separated from the foreign waste materials withoutpropelling the solvent upwardly toward drain 18 or unnecessarilyatomizing it. Since the filter receptacle 32 is positioned with theinterior cavity 77 of the collar 72, when the solvent 26 is forcedthrough the filter element 34 and the perforated filter side wall 82during operation of the parts washing apparatus 10, the solvent willeither drop directly into the solvent reservoir 14 or be deflected intothe solvent reservoir 14 by the interior surface 73 of the collar 72.

Returning to FIG. 1, the pump 22 is removably attached by a pumpextension 108 to the longitudinal member 92 through a hole which can bepositioned anywhere on the longitudinal member 92, as long as the pumpmounting extension 108 does not interfere with either the belt 102 orthe pulleys 100, 105.

In FIG. 5, the attachment of the mounting bracket 27 to the collar 72 isillustrated. A support member 110 is attached to either side of thelongitudinal member 92 so that each of the support members 110 extendsupwardly to a point where its upper end 111 is removably connected to abracket 112 that has been attached to the collar 72. It should be notedthat slight modifications of the mounting bracket can be made by thoseskilled in the art to attach the centrifugal filter assembly 16 to manyof the parts washers currently in use or on the market. These “adapted”mounting brackets are included with the remainder of the centrifugalfilter assembly 16, described above, as the primary components in aretrofit kit to transform existing parts washers into the presentinvention. Secondary filter means 136 and tertiary filter means 148 arealso preferably included with the retrofit kit, but can be deleted ifalready included on the existing parts washer.

In the preferred embodiment, two design features enable the filterreceptacle to more efficiently use centrifugal force to separate thesolvent from the waste. The first modification helps retain the solventinside the filter receptacle until centrifugal force draws it throughthe filter media and the perforated side walls. Referring to FIG. 2,this is done by slightly slanting the perforated side wall 82 in afrusto-conical configuration upwardly and inwardly from the base 84 tothe open top end 80. This upward and inward slant is preferably 12 to 14degrees inwardly toward the vertical axis 106. The second design featureemploys a deflecting member 118 that has a top rounded center portion119 and a downwardly extending skirt 121 that slants outwardly from thevertical axis 106. The deflecting member 118 is attached to, or formedintegrally from, the center 119 of the interior upward facing portion 86of the base member 84. The purpose of the deflecting member 118 is todirect the solvent outwardly toward the side wall 82 and away from thecenter 119 of the filter receptacle 32 where the centripetalacceleration approaches zero and the solvent is less likely to beaffected by the corresponding centrifugal force.

During normal use, a disposable filter element 34 is draped inside thefilter receptacle 32. Referring to FIG. 6, the upper open portion 126 ofthe disposable filter element 34 contains a securing means 127 that isfolded over the open top portion 126 of the filter receptacle 32. Thesecuring means 127, for instance, can be a string or elastic fiber thatis sown into a channel 129 on the upper portion 126 of the disposablefilter element 34. The lower closed portion 128 of the filter elementdrapes over the deflecting member 118. Preferably, the disposable filterelement 34 is approximately the same size as the interior 109 of thefilter receptacle 32, so that, when the filter receptacle 32 isspinning, the walls 130 of the disposable filter element 34 will clingto the filter side wall 82. The disposable filter element 34 ispreferably made from a fine mesh linen cloth, although other filtermedia would work, for instance, a heavy, permeable paper filter. Thepreferred embodiment of the invention presently uses a 100 micron meshlinen for its filter media.

Returning to FIG. 3, the removable filter element 34 is accessed forservice through a hatch 132 positioned above the filter receptacle 32 inthe bottom portion of the sink 36. As shown in FIG. 3, the hatch 132 iscircular and concentrically surrounds and includes the drain 18. Thehatch lies in a round opening in the sink bottom wall 40 that has acircumferential lip that is formed lower than the upper surface of thesink bottom wall 40 in order to contain the circular hatch 132 (FIG. 1).The hatch 132 can be secured to the sink 36 with one or more screws 138or can just rest in the indentation 134. A screen 142 usually covers thedrain 18 and is particularly useful for keeping needed components of thepart being washed from being flushed into the centrifugal filterassembly 16. In FIG. 3, the screen 142 is in the form of a disk thatrests inside a circumferential indentation 143 (FIG. 1) that surroundsthe drain 18. FIG. 2 shows another screen 144 that is formed into theshape of a cup and also rests in the circumferential indentation 143that surrounding the drain 18. The cup screen 144 has an upper lipportion 141 that is held in indentation 143. It also has a bottomportion 145 with a contiguous circumferential side wall 147 that areboth formed from a screen material that will retain relatively largepieces of foreign material that are washed from parts while passing thesolvent and smaller foreign materials. Depending on the preference ofthe user, the disk configuration screen 142, the cup configurationscreen 144, both, or neither, can be placed in the drain 18. Together,the screens 142, 144, comprise the secondary filter assembly 136.

A tertiary filter assembly 148 used to polish the solvent before beingintroduced to the parts washing basin 12 can optionally be included. Thetertiary filter assembly 148 is one of common design and comprises afilter housing 150, a filter media 154 inside the filter housing, afilter cap 152 to seal the filter housing, an inlet 156 connected to thepump side 158 of the solvent transfer means 20, and an outlet 160connected to the spigot side 162 of the solvent transfer means 20. Thefilter media usually takes the form of a filter cartridge comprised of afan-folded permeable paper material, although many other filter mediacould be used.

As mentioned above, existing parts washers can be adapted to the presentinvention by using a retrofit fit kit comprising a centrifugal filterassembly 16 with a mounting bracket 27 specially adapted to mount thecentrifugal filter assembly 16 to the existing parts washer. Theretrofit kit also preferably includes the secondary filter assembly 136and the tertiary filter assembly 148.

An existing parts washer will typically have a parts washing basin 12, adrain 18, and a collar 72 that are similar to those illustrated in FIG.1. As in the present invention, the centrifugal filter assembly 16 ismounted below the drain 18 of the existing parts washer by connectingbracket 112 either to the collar 72 or to the underside portion 70 ofthe parts washing basin 12. Generally, bracket 112 has two ends joinedat an angle to each other with a first end 113 attached to the upper end111 of the support member 110 and the second end having a hole toreceive a mounting bolt extending from the existing parts washer.

To mount the centrifugal filter assembly 10 to collar 72, for instance,the second end of bracket 112 could be specifically configured to alignwith a hole drilled in collar 72 by the retrofit installer. Bracket 112is then bolted to collar 72 through these aligned holes. Similarly,bracket 112 could be rotated ninety degrees so that the second end ofthe bracket is substantially parallel to the sink bottom 40 and alignedwith a hole drilled by the installer in the sink bottom 40. Bracket 112is then bolted to sink bottom 40. A washer is placed around the mountingbolt passing through the sink bottom 40 and the bracket 112 to preventsolvent leakage through the hole. Bracket 112, therefore, can be thoughtof as an adapter for mounting the centrifugal filter assembly 10 to theexisting parts washer. By altering its shape to conform to the existingparts washer and its length to properly position the centrifugal filterassembly 10 below drain 18, almost any existing parts washer couldretrofitted to the present invention. Of course, bracket 112 could beomitted and the mounting bracket 27 could be specifically adapted forsupport member 110 to be attached to each type of existing parts washer.By altering the length of bracket 112, support 110, the transversemember 94 and the longitudinal member 92, the centrifugal filterassembly can be properly positioned in almost all existing partswashers. In any case, the means of attachment preferably allows thecentrifugal filter 10 assembly to be removed while replacing filterelement 34.

The pump 22 on the existing parts washer can be left in place if it doesnot obstruct the installation of the centrifugal filter assembly 10.Otherwise, the pump 22 is removed and then suspended by pump mountingextension 108 from mounting bracket 27, as is described above. The pump22 and the motor 96 are electrically connected in parallel with theelectrical wires passing through access 72. To complete the retrofit,the secondary filter means 136 is placed in drain 18 and the tertiaryfilter is connected in series with the solvent transfer means 20, in thesame manner as is described above.

The ease of maintenance of the parts washing apparatus 10 is one of theprimary design benefits resulting from the teaching of this application.To clean the apparatus 10, the user first removes the disk screen 142and/or the cup screen 144 from the drain 18. The user then removes thehatch 132 from the bottom portion of the sink portion 36, exposing thefilter receptacle 32 and the disposable filter media 34. At this point,the user can dump the contents of the screens 142, 144 into thedisposable filter element 34, or the user can do the same after thedisposable filter element 34 is removed. If necessary, the securingmeans of the disposable filter element 34 is loosened and the disposablefilter element 34 is lifted from the filter receptacle 32. Because ofthe centrifugal force placed on the disposable filter 34 element duringits use, the disposable filter element 34 and its contents should bemostly free of solvent. The used disposable filter element 34 is thenplaced in a container to be processed by a solvent service provider. Thedisposable filter media in the tertiary filter 148 can also be removedat this time and placed in the reprocessing container. The user thenreplaces the disposable filter element from the tertiary filter 148 inthe filter receptacle, re-installs the hatch 132 and replaces screens142, 144. If the tertiary filter 148 has been serviced, a new disposablefilter element is placed in the tertiary filter 148 and the cap 152replaced.

The entire service procedure on the parts washing apparatus 10 can beaccomplished in a few minutes. The hazardous waste products removed fromthe system are all contained in the disposable filter element 34 and thedisposable filter element of the tertiary filter assembly 148. Thisrelatively small volume of hazardous waste material is sealed in a smalland light container that is mostly free of solvent and that can easilyand safely be transported to a hazardous waste processing plant. Thesolvent 26 remains relatively free of contaminants and may be re-usedfor a much greater length of time than is now possible under the stateof the art.

While this invention has been described in terms of a preferredembodiment, it is contemplated that persons reading the precedingdescription and studying the drawing will realize various alterations,permutations and modifications thereof. It is therefore intended thatthe following appended claims be interpreted as including all suchalterations and modifications as fall within the true spirit and scopeof the present invention.

What is claimed is:
 1. A method of cleaning parts with a solvent whilemaintaining a relatively high degree of purity of the solvent, saidmethod comprising: a) placing the parts to be washed in a wash basin; b)causing the parts to be washed with solvent in the wash basin; c)directing the solvent from the wash basin to flow by the force ofgravity from the wash basin to a centrifugal filter and operating thecentrifugal filter to separate from the solvent impurities in thesolvent; d) collecting the solvent separated from the centrifugal filterin a reservoir; e) recirculating the solvent from the reservoir back tothe wash basin for further use in washing parts in the wash basin. 2.The method as recited in claim 1, wherein there is a submersible pump insolvent that is contained in the reservoir, said method comprisingoperating said pump to discharge solvent from the reservoir upwardly andinto the wash basin.
 3. The method as recited in claim 1, comprisingpositioning a replaceable filter element in a rotatably mountedreceptacle structure of the centrifugal filter and collecting impuritiesin the replaceable filter element.
 4. The method as recited in claim 3,wherein the replaceable filter element with impurities therein isperiodically removed from the receptacle structure for disposal, andanother replaceable filter element positioned in the receptaclestructure.
 5. The method as recited in claim 1, wherein solvent flows bygravity from the wash basin into an upwardly directed opening of thecentrifugal filter.
 6. The method as recited in claim 1, wherein thesolvent is directed into the centrifugal filter to engage a solventdeflecting member which directs the solvent outwardly toward a radiallyoutward portion of the centrifugal filter.
 7. The method as recited inclaim 1, wherein the centrifugal filter comprises a receptacle structurehaving a circumferential wall which slants downwardly and radiallyoutwardly from a center axis of rotation, and said solvent is caused bycentrifugal force to flow downwardly in the centrifugal filter andoutwardly.
 8. The method as recited in claim 1, wherein the solvent iscaused to flow from the centrifugal filter to the reservoir by gravityflow.
 9. The method as recited in claim 1, wherein there is a hoodmember for said wash basin, said method comprising placing said hoodmember at a location relative to said wash basin so that the hood membercan be placed over the wash basin in the event of a fire occurring inthe wash basin.
 10. The method as recited in claim 9, further comprisingpositioning the hood member in an open position and holding the hoodmember in the open position by a fusible link, with said fusible linkbeing arranged to give way in the event of a solvent fire in the basinto permit the hood member to close over the wash basin.
 11. The methodas recited in claim 1, further comprising surrounding said centrifugalfilter with an enclosure wall to contain solvent discharged from thefilter.
 12. The method as recited in claim 1, wherein the centrifugalfilter comprises a sludge containing member that has a containing walldefining a containing region, said containing member being removablymounted, said method further comprising removing said containing memberperiodically for disposal of impurities collected therein.
 13. Themethod as recited in claim 12, further comprising providing saidcontainer member as a permeable material to retain the impurities andpermit the solvent to pass therethrough.
 14. The method as recited inclaim 13, wherein said permeable member is provided as a bag made of apermeable material, said method further comprising removing said bagcontaining the collected impurities.
 15. A method of cleaning parts witha solvent while maintaining a relatively high degree of purity of thesolvent, said method comprising: a) placing the parts to be washed in awash basin; b) causing the parts to be washed with solvent in the washbasin; c) directing the solvent from the wash basin through a drain inthe wash basin to a centrifugal filter and operating the centrifugalfilter to separate from the solvent impurities in the solvent; d)collecting the solvent separated from the centrifugal filter in areservoir; e) recirculating the solvent in the reservoir by utilizing apump to recirculate the solvent in the reservoir through a recirculatingline back to the wash basin for further use in washing parts in the washbasin.
 16. The method as recited in claim 15, wherein the solvent flowsthrough the drain and to the centrifugal filter by force of gravity. 17.The method as recited in claim 15, wherein there is a submersible pumpin solvent that is contained in the reservoir, said method comprisingoperating said pump to discharge solvent from the reservoir upwardly andinto the wash basin.
 18. The method as recited in claim 15, comprisingpositioning a replaceable filter element in a rotatably mountedreceptacle structure of the centrifugal filter and collecting impuritiesin the replaceable filter element.
 19. The method as recited in claim18, wherein the replaceable filter element with impurities therein isperiodically removed from the receptacle structure for disposal, andanother replaceable filter element positioned in the receptaclestructure.
 20. The method as recited in claim 15, wherein solvent flowsby gravity from the wash basin into an upwardly directed opening of thecentrifugal filter.
 21. The method as recited in claim 15, wherein thesolvent is caused to flow from the centrifugal filter to the reservoirby gravity flow.